Re: Window system dependant parts of gtk (sources), Win32integration

[Christiaan Welvaart <C J Welvaart phys uu nl>]

On 26 Nov 1998, Owen Taylor wrote:

> A few techniques that can be used instead of large-scale
> #ifdef's.
> 
>  1) Conditionally include files including window-specific 
>     implementations. (I.e., Raph's suggestion)
>
>  2) Have win32 and unix variants of a few key files, and
>     use a different set of files for the Win32 build.
>
>  3) Figure out a way of abstracting a window-system 
>     dependency to the GDK level. (This is probably the
>     most productive, if most difficult, strategy)

Code duplication should be prevented, I guess, so I don't really see the
difference between these three approaches (1 & 2 are ways to implement 3).

If I see it right, GDK contains a lot of functionality by it self, so a
separate window-system dependent layer would be nice. This isn't too
difficult either, since X-specific code is concentrated in a few places,
and is sometimes already put in functions. I don't know if Tor is working
on this, but here are my two cents. (I'm interested in this because I plan
to do a MacOS port of GTK.)


One could define a set of window-system dependent functions, that are
called at fixed points in the GDK code. For example gdk_init does
initialisation of both the internal GDK administration and the window
system. If the current X-dependent code is moved to a function
gdk_init_xwindows, the choice between different window-systems could be
abstracted into a macro. (Is this a good way to do this?) The macro I used
(defined in config.h) is:

#if defined(DISPLAY_XWINDOWS)
#define DISPLAY_SPECIFIC(name) name##_xwindows
#elif defined(DISPLAY_WIN32)
#define DISPLAY_SPECIFIC(name) name##_win32
<and so on>
#endif

"problems":
 - Function calls look a bit funny this way, like
     DISPLAY_SPECIFIC(gdk_init)();
     DISPLAY_SPECIFIC(gdk_event_tranlate)(event);
 - no run-time choice between window-systems possible

"advantages":
 - many source files can be made window-system independent (the
   preprocessor adds the dependencies)
 - when the display specific functions are defined as inline, there won't
   be much difference with current code after compilation


I'm halfway implementing this in gdk.c, and I didn't find any real
problems, which doesn't prove anything, though... Is this of any use for
GTK?



    Christiaan